adds a xul overlay to mochikit.manifest to load up the chrome half of the test harness

sends –log-file (init, log, close) function calls through a dispatchEvent into messageManager.loadFrameScript code. Event listener then calls the same init, log, close functions and has access to write to a file.

sends quit message through dispatchEvent into messageManager.loadFrameScript code which then sends a message to chrome (proper) which does the quit.

Originally this patch was intended to include the overlay on all mochitest style testing (chrome, browser-chrome, a11y, plain) but we ran into issues with the focus code when chrome tests would open a new window (the ipc listening code was not loaded, so events would be dispatched but not received). The code is not needed for anything but mochitest-plain, which is why we only use it there.

There is still a lot of work to be done in order to get these tests running green on a Firefox desktop build with IPC. The target for this month was getting it running in general which will be used for Fennec (about 85% of the test files run successfully now). Here are a few things we need to resolve for complete runs: